I don't see why not......I would say that you can use any type of cartridges. to make pens ....But what type of shell is he thinking of ?????? .35 Rem? .35 whelen?? 356 Winchester???? 358 Winchester???. 350 Remington Magnum????? .358 Norma Magnum????
all of these use .358" diameter....or should I say 35 cal bullets ....also pistol shells such as.....38 special, and .357 magnum, also use the same diameter bullet.
If your friend was talking about .35 Remington, and if you need some brass I may be able to help you.